Semiconductor storage device

ABSTRACT

A semiconductor storage device includes first and second stacked bodies, a first semiconductor layer, a first charge storage layer, a conductive layer, and a first silicon oxide layer. The first stacked body includes first insulation layers and first gate electrode layers that are alternately stacked in a first direction. The first semiconductor layer extends in the first stacked body in the first direction. The first charge storage layer is provided between the first semiconductor layer and the first gate electrode layers. The conductive layer is provided between the first stacked body and the second stacked body and extends in the first direction and a second direction. The first silicon oxide layer is provided between the conductive layer and the first gate electrode layers. The first silicon oxide layer containing an impurity being at least one of phosphorus, boron, carbon, and fluorine.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2020-049901, filed on Mar. 19, 2020, the entire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a semiconductor storage device.

BACKGROUND

A three-dimensional NAND flash memory in which memory cells are stacked three-dimensionally achieves a high degree of integration and has low costs. In the three-dimensional NAND flash memory, a memory hole passing through a stacked body is formed. The stacked body is formed by alternately stacking an insulation layers and an electrode layers. A charge storage layer and a semiconductor layer are formed in the memory hole, thereby forming a memory string in which a plurality of memory cells are connected in series. Data is stored in the memory cells by controlling an amount of charges retained in the charge storage layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a schematic cross-sectional view of a memory cell array of a semiconductor storage device according to a first embodiment.

FIG. 2 illustrates an enlarged schematic cross-sectional view of a part of a memory cell array of a semiconductor storage device according to a first embodiment.

FIG. 3 illustrates an enlarged schematic cross-sectional view of a part of a memory cell array of a semiconductor storage device according to a first embodiment.

FIGS. 4-13 are schematic cross-sectional diagrams to explain a method for manufacturing a semiconductor storage device according to a first embodiment.

FIG. 14 illustrates an enlarged schematic cross-sectional view of a part of a memory cell array of a semiconductor storage device according to a second embodiment.

FIG. 15 illustrates an enlarged schematic cross-sectional view of a part of a memory cell array of a semiconductor storage device according to a third embodiment.

FIG. 16 illustrates an enlarged schematic cross-sectional view of a part of a memory cell array of a semiconductor storage device according to a fourth embodiment.

DETAILED DESCRIPTION

In general, according to an embodiment, a semiconductor storage device includes first and second stacked bodies, first and second semiconductor layers, first and second charge storage layers, a conductive layer, and a first silicon oxide layer. The first stacked body includes a plurality of first insulation layers and a plurality of first gate electrode layers that are alternately stacked in a first direction. The first semiconductor layer extends in the first stacked body in the first direction. The first charge storage layer is provided between the first semiconductor layer and the plurality of first gate electrode layers. The second stacked body includes a plurality of second insulation layers and a plurality of second gate electrode layers that are alternately stacked in the first direction. The second semiconductor layer extends in the second stacked body in the first direction. The second charge storage layer is provided between the second semiconductor layer and the plurality of second gate electrode layers. The conductive layer is provided between the first stacked body and the second stacked body and extending in the first direction and a second direction perpendicular to the first direction. The first silicon oxide layer is provided between the conductive layer and the plurality of first gate electrode layers. The first silicon oxide layer containing an impurity including at least one of phosphorus (P), boron (B), carbon (C), and fluorine (F).

Hereinafter, certain example embodiments will be described with reference to drawings. In the following description, the same or substantially similar components or aspects are denoted by the same reference numerals, and description of the components or aspect already described may be omitted.

In the present specification, terms “up” or “down” or the like may be used for convenience of description. However, in this context such terms as “up” or “down” are terms indicating, a relative positional relationship between components or aspects in the drawings or the like. The terms “up” and “down” do not necessarily reflect any orientation or a positional relationship with respect to gravity.

Qualitative and quantitative analyses for analyzing chemical composition of components or aspects constituting a semiconductor storage device in the present specification may be performed using secondary ion mass spectrometry (SIMS), energy dispersive X-ray spectroscopy (EDX), and the like. A transmission electron microscope (TEM) or the like may be used to measure a thickness of a component or aspect of the semiconductor storage device, a distance between components or aspects, and the like.

First Embodiment

A semiconductor storage device according to a first embodiment includes a first stacked body formed by alternately stacking first insulation layers and first gate electrode layers in a first direction. A first semiconductor layer is provided in the first stacked body and extends in the first direction. A first charge storage layer is provided between the first semiconductor layer and first gate electrode layers. A second stacked body is formed by alternately stacking second insulation layers and second gate electrode layers in the first direction. A second semiconductor layer is provided in the second stacked body and extends in the first direction. A second charge storage layer is provided between the second semiconductor layer and the second gate electrode layers. A conductive layer is provided between the first stacked body and the second stacked body and extends in the first direction and a second direction perpendicular to the first direction. A first silicon oxide layer is provided between the first gate electrode layers and the conductive layer and contains at least one element selected from a group of elements including phosphorus (P), boron (B), carbon (C), and fluorine (F).

The semiconductor storage device according to the first embodiment is a three-dimensional NAND flash memory. A memory cell of the semiconductor storage device according to the first embodiment is a so-called Metal-Oxide-Nitride-Oxide-Semiconductor (MONOS) memory cell.

FIG. 1 illustrates a schematic cross-sectional view of a memory cell array of the semiconductor storage device according to the first embodiment. A wire layer on an upper part of a memory cell array 100 is omitted from the depiction in FIG. 1 .

The memory cell array 100 includes a silicon substrate 10, a plurality of stacked bodies 12, a plurality of memory strings 14, conductive layers 16, and silicon oxide layers 18. The silicon substrate 10 is an example of a semiconductor substrate.

The stacked body 12 is formed by alternately stacking interlayer insulation layers 20 and gate electrode layers 22 in a first direction. The first direction is a normal to a surface of the silicon substrate 10.

The plurality of memory strings 14 pass through the stacked body 12. The memory strings 14 are provided in memory holes passing through the stacked body 12. The memory strings 14 extend in the stacked body 12 in the first direction. One memory string 14 and the plurality of gate electrode layers 22 form a plurality of memory cells.

The conductive layer 16 is provided between two stacked bodies 12. The conductive layer 16 passes through the stacked bodies 12. The conductive layer 16 extends in the stacked bodies 12 in the first direction. The conductive layer 16 is in contact with the silicon substrate 10. The conductive layer 16 has a function of applying a voltage to a lower end of the memory string 14 via the silicon substrate 10.

The silicon oxide layer 18 is provided between the conductive layer 16 and the stacked body 12. The silicon oxide layer 18 has a function of electrically separating the conductive layer 16 and the gate electrode layer 22.

FIGS. 2 and 3 illustrate enlarged schematic cross-sectional views of parts of the memory cell array of the semiconductor storage device according to the first embodiment. FIG. 2 illustrates a cross-sectional view taken along AA′ in FIG. 3 . FIG. 3 illustrates a cross-sectional view taken along BB′ in FIG. 2 . A region surrounded by a dotted line corresponds to one memory cell in FIGS. 2 and 3 .

The memory cell array 100 includes a first stacked body 12 a, a second stacked body 12 b, the conductive layer 16, a first silicon oxide layer 18 a, a second silicon oxide layer 18 b, a plurality of first interlayer insulation layers 20 a, a plurality of second interlayer insulation layers 20 b, a plurality of first gate electrode layers 22 a, a plurality of second gate electrode layers 22 b, a first semiconductor layer 24 a, a second semiconductor layer 24 b, a first charge storage layer 26 a, a second charge storage layer 26 b, a first core insulation layer 28 a, a second core insulation layer 28 b, a first aluminum oxide layer 30 a, and a second aluminum oxide layer 30 b.

The first interlayer insulation layer 20 a is an example of a first insulation layer. The second interlayer insulation layer 20 b is an example of a second insulation layer. The first aluminum oxide layer 30 a is an example of an aluminum oxide layer.

The first stacked body 12 a is formed by alternately stacking first interlayer insulation layers 20 a and first gate electrode layers 22 a in the first direction.

The first gate electrode layer 22 a is, for example, a metal layer. The first gate electrode layer 22 a includes, for example, tungsten (W). The first gate electrode layer 22 a may have, for example, a structure in which a plurality of metal layers are stacked. The first gate electrode layer 22 a has, for example, a structure in which a layer of titanium nitride (TiN) and a layer of tungsten (W) are stacked. A thickness of the first gate electrode layer 22 a in the first direction is, for example, 5 nm to 20 nm.

The first interlayer insulation layer 20 a electrically separates two otherwise adjacent first gate electrode layers 22 a. The first interlayer insulation layer 20 a is, for example, silicon oxide. A thickness of the first interlayer insulation layer 20 a in the first direction is, for example, 5 nm to 20 nm.

The first semiconductor layer 24 a, the first charge storage layer 26 a, and the first core insulation layer 28 a form one memory string 14 in the first stacked body 12 a.

The first semiconductor layer 24 a extends in the first stacked body 12 a in the first direction. The first semiconductor layer 24 a passes through the first stacked body 12 a. The first stacked body 12 a is surrounded by a plurality of first gate electrode layers 22 a. The first semiconductor layer 24 a has, for example, a cylindrical shape. The first semiconductor layer 24 a functions as a channel of a transistor of a memory cell.

The first semiconductor layer 24 a is, for example, a polycrystalline semiconductor. The first semiconductor layer 24 a is, for example, polycrystalline silicon.

The first charge storage layer 26 a is provided between the first semiconductor layer 24 a and the first gate electrode layer 22 a. The first charge storage layer 26 a includes a tunnel insulation film, a charge trapping film, a block insulation film, and the like from a first semiconductor layer 24 a side. The charge trapping film is provided between the tunnel insulation film and the block insulation film. The tunnel insulation film, the charge trapping film, and the block insulation film are, for example, a silicon oxide film, a silicon nitride film, and a silicon oxide film, respectively.

The tunnel insulation film has a function of selectively causing charges to pass through. The charge trapping film has a function of trapping and storing charges. The block insulation film has a function of blocking a current flowing between the charge trapping film and the first gate electrode layer 22 a. The memory cell is a so-called MONOS memory cell.

The first charge storage layer 26 a is provided along a side surface of the first semiconductor layer 24 a. The first charge storage layer 26 a may be divided between adjacent memory cells in the first direction.

A threshold voltage of a transistor of a memory cell changes according to an amount of charges stored in the first charge storage layer 26 a. Data can be stored in one memory cell by using a change in the threshold voltage.

For example, a voltage at which the transistor is turned on can be changed by changing the threshold voltage of the transistor of the memory cell. For example, when a state in which the threshold voltage is high is defined as data “0” and a state in which the threshold voltage is low is defined as data “1”, the memory cell can store one bit data of “0” and “1” (binary data).

The first core insulation layer 28 a is surrounded by the first semiconductor layer 24 a. The first core insulation layer 28 a extends in the first direction. The first core insulation layer 28 a is, for example, a silicon oxide layer.

The second stacked body 12 b is formed by alternately stacking a plurality of second interlayer insulation layers 20 b and a plurality of second gate electrode layers 22 b in the first direction.

The second semiconductor layer 24 b, the second charge storage layer 26 b, and the second core insulation layer 28 b form one memory string 14 in the second stacked body 12 b.

The second semiconductor layer 24 b extends in the second stacked body 12 b in the first direction. The second semiconductor layer 24 b passes through the second stacked body 12 b.

The second charge storage layer 26 b is provided between the second semiconductor layer 24 b and the second gate electrode layer 22 b.

The second core insulation layer 28 b is surrounded by the second semiconductor layer 24 b. The second core insulation layer 28 b extends in the first direction.

The second interlayer insulation layer 20 b, the second gate electrode layer 22 b, the second semiconductor layer 24 b, the second charge storage layer 26 b, and the second core insulation layer 28 b have configurations and functions respectively the same as those of the first interlayer insulation layer 20 a, the first gate electrode layer 22 a, the first semiconductor layer 24 a, the first charge storage layer 26 a, and the first core insulation layer 28 a.

The conductive layer 16 is provided between the first stacked body 12 a and the second stacked body 12 b. The conductive layer 16 extends in the first direction and the second direction perpendicular to the first direction. The conductive layer 16 has, for example, a plate shape. The conductive layer 16 is in contact with the silicon substrate 10.

The conductive layer 16 is, for example, a metal layer or a semiconductor layer. The conductive layer 16 contains, for example, tungsten (W). The conductive layer 16 may have, for example, a structure in which a plurality of metal layers are stacked. The conductive layer 16 has, for example, a structure in which a layer of titanium nitride (TiN) and a layer of tungsten (W) are stacked.

The first silicon oxide layer 18 a is provided between the first stacked body 12 a and the conductive layer 16. The first silicon oxide layer 18 a is provided between the first gate electrode layer 22 a and the conductive layer 16. The first silicon oxide layer 18 a is in contact with the first gate electrode layer 22 a. The first silicon oxide layer 18 a is in contact with the conductive layer 16. The first silicon oxide layer 18 a is provided between the first interlayer insulation layer 20 a and the conductive layer 16.

The first silicon oxide layer 18 a has a function of electrically separating the first gate electrode layer 22 a and the conductive layer 16.

The first silicon oxide layer 18 a contains silicon oxide as a main component. The main component of silicon oxide refers to that silicon oxide has a highest mole fraction among components contained in the first silicon oxide layer 18 a.

The first silicon oxide layer 18 a contains, as an impurity, at least one element selected from a group including phosphorus (P), boron (B), carbon (C), and fluorine (F). The first silicon oxide layer 18 a is a silicon oxide layer containing, in an example, phosphorus (P). The first silicon oxide layer 18 a is a silicon oxide layer containing, in another example, boron (B). The first silicon oxide layer 18 a is a silicon oxide layer containing, in another example, carbon (C). The first silicon oxide layer 18 a is a silicon oxide layer containing, in another example, fluorine (F).

A concentration of the impurity contained in the first silicon oxide layer 18 a is, for example, 1×10¹⁷ atoms/cm³ to 1×10²¹ atoms/cm³.

The concentration of the impurity contained in the first silicon oxide layer 18 a is, for example, higher than a concentration of the impurity in the first interlayer insulation layer 20 a.

The first aluminum oxide layer 30 a is provided between the first gate electrode layer 22 a and the first charge storage layer 26 a and between the first silicon oxide layer 18 a and the first interlayer insulation layer 20 a. The first aluminum oxide layer 30 a functions as a part of a block insulation film of a memory cell. The first aluminum oxide layer 30 a has a function of blocking a current flowing between the first charge storage layer 26 a and the first gate electrode layer 22 a.

The second silicon oxide layer 18 b is provided between the second stacked body 12 b and the conductive layer 16. The second silicon oxide layer 18 b is provided between the second gate electrode layer 22 b and the conductive layer 16. The second silicon oxide layer 18 b is in contact with the second gate electrode layer 22 b. The second silicon oxide layer 18 b is in contact with the conductive layer 16. The second silicon oxide layer 18 b is provided between the second interlayer insulation layer 20 b and the conductive layer 16.

The second silicon oxide layer 18 b has a function of electrically separating the second gate electrode layer 22 b and the conductive layer 16.

The second silicon oxide layer 18 b contains silicon oxide as a main component. The main component of silicon oxide refers to that silicon oxide has a highest mole fraction among components contained in the second silicon oxide layer 18 b.

The second silicon oxide layer 18 b contains, as an impurity, at least one element selected from a group including phosphorus (P), boron (B), carbon (C), and fluorine (F). The second silicon oxide layer 18 b is a silicon oxide layer containing, in an example, phosphorus (P). The second silicon oxide layer 18 b is a silicon oxide layer containing, in another example, boron (B). The second silicon oxide layer 18 b is a silicon oxide layer containing, in another example, carbon (C). The second silicon oxide layer 18 b is a silicon oxide layer containing, in another example, fluorine (F).

A concentration of the impurity contained in the second silicon oxide layer 18 b is, for example, 1×10¹⁷ atoms/cm³ to 1×10²¹ atoms/cm³.

The concentration of the impurity contained in the second silicon oxide layer 18 b is, for example, higher than a concentration of the impurity in the second interlayer insulation layer 20 b.

The second aluminum oxide layer 30 b is provided between the second gate electrode layer 22 b and the second charge storage layer 26 b and between the second silicon oxide layer 18 b and the second interlayer insulation layer 20 b. The second aluminum oxide layer 30 b functions as a part of a block insulation film of a memory cell. The second aluminum oxide layer 30 b has a function of blocking a current flowing between the second charge storage layer 26 b and the second gate electrode layer 22 b.

Next, an example of a method for manufacturing the semiconductor storage device according to the first embodiment will be described. Hereinafter, an example of a method for manufacturing the memory cell array 100 of the semiconductor storage device according to the first embodiment will be described.

FIGS. 4 to 13 are schematic cross-sectional diagrams to explain the method for manufacturing the semiconductor storage device according to the first embodiment. FIGS. 4 to 13 show cross-sectional structures corresponding to that shown in FIG. 2 .

First, silicon oxide films 50 and silicon nitride films 52 are alternately stacked on a semiconductor substrate (not shown) (FIG. 4 ). A structure is formed in which a plurality of silicon oxide films 50 and a plurality of silicon nitride films 52 were alternately stacked in the first direction.

The silicon oxide film 50 and the silicon nitride film 52 are formed by a chemical vapor deposition (CVD) method or the like. A part of the silicon oxide films 50 is finally manufactured into the first interlayer insulation layer 20 a and the second interlayer insulation layer 20 b.

Next, a memory hole 54 is formed in the silicon oxide films 50 and the silicon nitride films 52 (FIG. 5 ). The memory hole 54 passes through the silicon oxide films 50 and the silicon nitride films 52 and extends in the first direction. The memory hole 54 is formed by a lithography method, a reactive ion etching (RIE) method, and the like.

Next, a charge storage film 56, a polycrystalline silicon film 58, and a silicon oxide film 60 are formed inside the memory hole 54 (FIG. 6 ). The charge storage film 56 is, for example, a layered film of a silicon oxide film, a silicon nitride film, and a silicon oxide film. The charge storage film 56, the polycrystalline silicon film 58, and the silicon oxide film 60 are formed by a CVD method or the like.

The charge storage film 56 is formed into the first charge storage layer 26 a and the second charge storage layer 26 b. The polycrystalline silicon film 58 is formed into the first semiconductor layer 24 a and the second semiconductor layer 24 b. The silicon oxide film 60 is formed into the first core insulation layer 28 a and the second core insulation layer 28 b.

Next, an opening 62 is formed in the silicon oxide films 50 and the silicon nitride films 52 (FIG. 7 ). The opening 62 is formed by a lithography method, an RIE method, and the like.

Next, the silicon nitride films 52 are selectively removed by wet etching using the opening 62 as an etching groove (FIG. 8 ). In the wet etching, a phosphoric acid solution or the like is used to selectively etch the silicon nitride films 52 with respect to the silicon oxide films 50 and the charge storage film 56.

Next, aluminum oxide films 64 are formed in regions where the silicon nitride films 52 were removed (FIG. 9 ). The aluminum oxide films 64 are formed by a CVD method or the like. The aluminum oxide films 64 are formed into the first aluminum oxide layer 30 a and the second aluminum oxide layer 30 b.

Next, tungsten films 66 are formed (FIG. 10 ). The tungsten films 66 are formed by a CVD method or the like.

The tungsten films 66 are formed into the first gate electrode layer 22 a and the second gate electrode layer 22 b. A barrier metal film such as a titanium nitride film may be formed before the tungsten films 66 are formed.

Next, the tungsten films 66 on an inner wall of the opening 62 are removed (FIG. 11 ). The tungsten films 66 are removed by wet etching or the like.

Next, silicon oxide films 68 containing phosphorus (P) are formed on the inner wall of the opening 62 (FIG. 12 ). The silicon oxides films 68 are formed by a CVD method or the like. The silicon oxide films 68 are formed into the first silicon oxide layer 18 a and the second silicon oxide layer 18 b. The silicon oxide films 68 containing phosphorus (P) can also be formed by ion implanting phosphorus into a silicon oxide film containing no phosphorus after the silicon oxide film containing no phosphorus was formed by a CVD method.

Next, the opening 62 is filled with a tungsten film (FIG. 13 ). The tungsten film 70 is formed by a CVD method or the like.

The tungsten film 70 is formed into the conductive layer 16. A barrier metal film such as a titanium nitride film may be formed before the tungsten film 70 is formed.

The memory cell array 100 of the semiconductor storage device according to the first embodiment can be manufactured according to the manufacturing method described above.

Next, functions and effects of the semiconductor storage device according to the first embodiment will be described.

In a three-dimensional NAND flash memory, a charge retention property of a memory cell close to an end portion of a stacked body that constitutes a memory cell array may deteriorate significantly. Due to the deterioration of the charge retention property, a data retention failure may occur in the memory cell close to an end portion of a stacked body. The deterioration of the charge retention property of the memory cell close to an end portion of a stacked body is significant particularly when a conductive layer was provided in a region between two stacked bodies.

According to a study result of an inventor, it was found that the deterioration of the charge retention property of the memory cell close to an end portion of a stacked body is prevented by providing a silicon oxide layer containing, as an impurity, at least one element selected from a group including phosphorus (P), boron (B), carbon (C), and fluorine (F) between the end portion of the stacked body and the conductive layer.

In the memory cell array 100 of the semiconductor storage device according to the first embodiment, the first silicon oxide layer 18 a containing, as an impurity, at least one element selected from a group including phosphorus (P), boron (B), carbon (C), and fluorine (F) is provided between the first stacked body 12 a and the conductive layer 16. The first silicon oxide layer 18 a is provided between the first gate electrode layer 22 a and the conductive layer 16.

The second silicon oxide layer 18 b containing, as an impurity, at least one element selected from a group including phosphorus (P), boron (B), carbon (C), and fluorine (F) is provided between the second stacked body 12 b and the conductive layer 16. The second silicon oxide layer 18 b is provided between the second gate electrode layer 22 b and the conductive layer 16.

As a result, deterioration of the charge retention property of the memory cell close to an end portion of a stacked body is prevented and occurrence of a data retention failure is prevented in the semiconductor storage device according to the first embodiment. Therefore, a semiconductor storage device capable of improving a charge retention property can be implemented according to the first embodiment.

Movable ions are considered as a factor that causes significant deterioration of a charge retention property of the memory cell close to an end portion of a stacked body. Since movable ions such as sodium (Na) and potassium (K) in a memory cell array are trapped in a charge storage layer of the memory cell, a charge retention property of the memory cell may deteriorate. Movable ions enter a memory cell array related to a formation process of a conductive layer, a structure of a conductive layer, or the like, and a charge retention property of a memory cell may deteriorate.

It is known that silicon oxide containing phosphorus (P), for example, has an ability of gettering sodium (Na) or potassium (K). Movable ions can be fixed by the first silicon oxide layer 18 a and the second silicon oxide layer 18 b, and deterioration of a charge retention property of a memory cell can be prevented.

In terms of preventing the deterioration of a charge retention property of a memory cell, concentrations of the impurity contained in the first silicon oxide layer 18 a and the second silicon oxide layer 18 b are each preferably 1×10¹⁷ atoms/cm³ or more, and even more preferably 1×10¹⁸ atoms/cm³ or more.

In terms of preventing a leakage current between the first gate electrode layer 22 a and the conductive layer 16 and between the second gate electrode layer 22 b and the conductive layer 16, concentrations of the impurity contained in the first silicon oxide layer 18 a and the second silicon oxide layer 18 b are respectively preferably 1×10²¹ atoms/cm³ or less.

As described above, a semiconductor storage device capable of improving a charge retention property can be provided according to the first embodiment.

Second Embodiment

A semiconductor storage device according to a second embodiment is different from the semiconductor storage device according to the first embodiment in that a first silicon oxide layer includes a first region and a second region provided in at least between the first region and a first gate electrode layer or between the first region and a conductive layer, and a concentration of at least one element in the first region is higher than a concentration of at least one element in the second region. Other aspects of the second embodiment are the same or substantially similar to the first embodiment.

The semiconductor storage device according to the second embodiment is a three-dimensional NAND flash memory. A memory cell of the semiconductor storage device according to the second embodiment is a so-called MONOS memory cell.

FIG. 14 illustrates an enlarged schematic cross-sectional view of a part of a memory cell array of the semiconductor storage device according to the second embodiment.

A memory cell array 200 includes the first stacked body 12 a, the second stacked body 12 b, the conductive layer 16, the first silicon oxide layer 18 a, the second silicon oxide layer 18 b, a plurality of first interlayer insulation layers 20 a, a plurality of second interlayer insulation layers 20 b, a plurality of first gate electrode layers 22 a, a plurality of second gate electrode layers 22 b, the first semiconductor layer 24 a, the second semiconductor layer 24 b, the first charge storage layer 26 a, the second charge storage layer 26 b, the first core insulation layer 28 a, the second core insulation layer 28 b, the first aluminum oxide layer 30 a, and the second aluminum oxide layer 30 b.

The first interlayer insulation layer 20 a is an example of a first insulation layer. The second interlayer insulation layer 20 b is an example of a second insulation layer. The first aluminum oxide layer 30 a is an example of an aluminum oxide layer.

The first silicon oxide layer 18 a includes a first high impurity concentration region 19 a and first low impurity concentration regions 19 b. The first high impurity concentration region 19 a is an example of a first region. The first low impurity concentration region 19 b is an example of a second region and/or a third region.

The first low impurity concentration region 19 b is provided between the first high impurity concentration region 19 a and the first gate electrode layer 22 a. The first low impurity concentration region 19 b is provided between the first high impurity concentration region 19 a and the conductive layer 16. The first high impurity concentration region 19 a is interposed between two first low impurity concentration regions 19 b.

The first high impurity concentration region 19 a contains, as an impurity, at least one element selected from a group including phosphorus (P), boron (B), carbon (C), and fluorine (F). A concentration of the impurity contained in the first high impurity concentration region 19 a is, for example, 1×10¹⁷ atoms/cm³ to 1×10²¹ atoms/cm³.

A concentration of the impurity contained in the first low impurity concentration region 19 b is, for example, less than 1×10¹⁷ atoms/cm³. The first low impurity concentration region 19 b may not contain the impurity.

The second silicon oxide layer 18 b includes a second high impurity concentration region 19 c and second low impurity concentration regions 19 d.

The second low impurity concentration region 19 d is provided between the second high impurity concentration region 19 c and the second gate electrode layer 22 b. The second low impurity concentration region 19 d is provided between the second high impurity concentration region 19 c and the conductive layer 16. The second high impurity concentration region 19 c is interposed between two second low impurity concentration regions 19 d.

The second high impurity concentration region 19 c contains, as an impurity, at least one element selected from a group including phosphorus (P), boron (B), carbon (C), and fluorine (F). A concentration of the impurity contained in the second high impurity concentration region 19 c is, for example, 1×10¹⁷ atoms/cm³ to 1×10²¹ atoms/cm³.

A concentration of the impurity contained in the second low impurity concentration region 19 d is, for example, less than 1×10¹⁷ atoms/cm³. The second low impurity concentration region 19 d may not contain the impurity.

According to the semiconductor storage device in the second embodiment, it is possible to optimally prevent deterioration of a charge retention property of a memory cell and a leakage current between the first gate electrode layer 22 a and the conductive layer 16 and between the second gate electrode layer 22 b and the conductive layer 16.

The first low impurity concentration region 19 b may be provided only either between the first high impurity concentration region 19 a and the first gate electrode layer 22 a or between the first high impurity concentration region 19 a and the conductive layer 16.

Similarly, the second low impurity concentration region 19 d may be provided only either between the second high impurity concentration region 19 c and the second gate electrode layer 22 b or between the second high impurity concentration region 19 c and the conductive layer 16.

As described above, a semiconductor storage device capable of improving a charge retention property can be provided according to the second embodiment. Further, it is possible to optimally prevent deterioration of a charge retention property of a memory cell and a leakage current between a gate electrode layer and a conductive layer.

Third Embodiment

A semiconductor storage device according to a third embodiment is different from the semiconductor storage device according to the first embodiment in that the semiconductor storage device according to the third embodiment further includes a third insulation layer provided between a first silicon oxide layer and a first gate electrode layer, and that the third insulation layer contains aluminum oxide or aluminum nitride. Other aspects of the third embodiment are the same or substantially similar to the first embodiment.

The semiconductor storage device according to the third embodiment is a three-dimensional NAND flash memory. A memory cell of the semiconductor storage device according to the third embodiment is a so-called MONOS memory cell.

FIG. 15 illustrates an enlarged schematic cross-sectional view of a part of a memory cell array of the semiconductor storage device according to the third embodiment.

A memory cell array 300 includes the first stacked body 12 a, the second stacked body 12 b, the conductive layer 16, the first silicon oxide layer 18 a, the second silicon oxide layer 18 b, a plurality of first interlayer insulation layers 20 a, a plurality of second interlayer insulation layers 20 b, a plurality of first gate electrode layers 22 a, a plurality of second gate electrode layers 22 b, the first semiconductor layer 24 a, the second semiconductor layer 24 b, the first charge storage layer 26 a, the second charge storage layer 26 b, the first core insulation layer 28 a, the second core insulation layer 28 b, the first aluminum oxide layer 30 a, the second aluminum oxide layer 30 b, a third aluminum oxide layer 32 a, and a fourth aluminum oxide layer 32 b.

The third aluminum oxide layer 32 a is an example of a third insulation layer.

The third aluminum oxide layer 32 a is provided between the first silicon oxide layer 18 a and the first gate electrode layer 22 a. The third aluminum oxide layer 32 a is provided between the first silicon oxide layer 18 a and the first interlayer insulation layer 20 a. The third aluminum oxide layer 32 a is provided between the first silicon oxide layer 18 a and the first aluminum oxide layer 30 a. The third aluminum oxide layer 32 a contains aluminum oxide.

The fourth aluminum oxide layer 32 b is provided between the second silicon oxide layer 18 b and the second gate electrode layer 22 b. The fourth aluminum oxide layer 32 b is provided between the second silicon oxide layer 18 b and the second interlayer insulation layer 20 b. The fourth aluminum oxide layer 32 b is provided between the second silicon oxide layer 18 b and the second aluminum oxide layer 30 b. The fourth aluminum oxide layer 32 b contains aluminum oxide.

Since the semiconductor storage device according to the third embodiment includes the third aluminum oxide layer 32 a, a charge retention property can be further improved. Since the semiconductor storage device according to the third embodiment includes the fourth aluminum oxide layer 32 b, a charge retention property can be furthermore improved.

A charge retention property can also be improved similarly by applying an insulation layer containing aluminum nitride instead of the third aluminum oxide layer 32 a or the fourth aluminum oxide layer 32 b.

As described above, a semiconductor storage device capable of improving a charge retention property can be provided according to the third embodiment. A semiconductor storage device capable of further improving the charge retention property can be provided.

Fourth Embodiment

A semiconductor storage device according to a fourth embodiment is different from the semiconductor storage device according to the first embodiment in that the semiconductor storage device according to the fourth embodiment further includes a fourth insulation layer provided between a first silicon oxide layer and a conductive layer, and that the fourth insulation layer contains aluminum oxide or aluminum nitride. Other aspects of the fourth embodiment are the same or substantially similar to the first embodiment.

The semiconductor storage device according to the fourth embodiment is a three-dimensional NAND flash memory. A memory cell of the semiconductor storage device according to the fourth embodiment is a so-called MONOS memory cell.

FIG. 16 illustrates an enlarged schematic cross-sectional view of a part of a memory cell array of the semiconductor storage device according to the fourth embodiment.

A memory cell array 400 includes the first stacked body 12 a, the second stacked body 12 b, the conductive layer 16, the first silicon oxide layer 18 a, the second silicon oxide layer 18 b, a plurality of first interlayer insulation layers 20 a, a plurality of second interlayer insulation layers 20 b, a plurality of first gate electrode layers 22 a, a plurality of second gate electrode layers 22 b, the first semiconductor layer 24 a, the second semiconductor layer 24 b, the first charge storage layer 26 a, the second charge storage layer 26 b, the first core insulation layer 28 a, the second core insulation layer 28 b, the first aluminum oxide layer 30 a, the second aluminum oxide layer 30 b, a fifth aluminum oxide layer 34 a, and a sixth aluminum oxide layer 34 b.

The fifth aluminum oxide layer 34 a is an example of a fourth insulation layer.

The fifth aluminum oxide layer 34 a is provided between the first silicon oxide layer 18 a and the conductive layer 16. The fifth aluminum oxide layer 34 a contains aluminum oxide.

The sixth aluminum oxide layer 34 b is provided between the second silicon oxide layer 18 b and the conductive layer 16. The sixth aluminum oxide layer 34 b contains aluminum oxide.

Since the semiconductor storage device according to the fourth embodiment includes the fifth aluminum oxide layer 34 a, a charge retention property can be further improved. Since the semiconductor storage device according to the fourth embodiment includes the sixth aluminum oxide layer 34 b, a charge retention property can be furthermore improved.

A charge retention property can also be improved similarly by applying an insulation layer containing aluminum nitride instead of the fifth aluminum oxide layer 34 a or the sixth aluminum oxide layer 34 b.

As described above, a semiconductor storage device capable of improving a charge retention property can be provided according to the fourth embodiment. A semiconductor storage device capable of further improving the charge retention property can be provided.

In the first to fourth embodiments, an interlayer insulation layer between gate electrode layers may be, for example, a cavity or a gap.

Although a memory cell of a MONOS structure was described as an example in the first to fourth embodiments, a memory cell of a floating gate structure using a conductive film may be applied instead of a charge trapping film of a charge storage layer or the like.

Although a structure in which one semiconductor layer is provided in each memory hole was described as an example in the first to fourth embodiments, a structure may be provided in which a plurality of semiconductor layers obtained by dividing the one semiconductor layer into two or more parts is provided in each memory hole. In such a structure, the number of memory cells in a stacked body may be doubled or more.

While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the disclosures. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the disclosures. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the disclosures. 

What is claimed is:
 1. A semiconductor storage device, comprising: a first stacked body including a plurality of first insulation layers and a plurality of first gate electrode layers that are alternately stacked in a first direction; a first semiconductor layer extending in the first stacked body in the first direction; a first charge storage layer between the first semiconductor layer and the plurality of first gate electrode layers; a second stacked body including a plurality of second insulation layers and a plurality of second gate electrode layers that are alternately stacked in the first direction; a second semiconductor layer extending in the second stacked body in the first direction; a second charge storage layer between the second semiconductor layer and the plurality of second gate electrode layers; a conductive layer between the first stacked body and the second stacked body and extending in the first direction and a second direction perpendicular to the first direction; and a first silicon oxide layer between the conductive layer and the plurality of first gate electrode layers, the first silicon oxide layer containing an impurity that is at least one of phosphorus, boron, carbon, and fluorine, wherein the first silicon oxide layer includes a first region and a second region between the first region and the plurality of first gate electrode layers, and a concentration of the impurity in the first region is higher than a concentration of the impurity in the second region.
 2. The semiconductor storage device according to claim 1, wherein a concentration of the impurity in the first silicon oxide layer is higher than a concentration of the impurity in the first insulation layer.
 3. The semiconductor storage device according to claim 1, wherein a concentration of the impurity in the first silicon oxide layer is in a range equal to or greater than 1×10¹⁷ atoms/cm³ and equal to or less than 1×10²¹ atoms/cm³.
 4. The semiconductor storage device according to claim 1, wherein a concentration of the impurity in the first region is in a range equal to or greater than 1×10¹⁷ atoms/cm³ and equal to or less than 1×10²¹ atoms/cm³, and a concentration of the impurity in the second region is in a range less than 1×10¹⁷ atoms/cm³.
 5. The semiconductor storage device according to claim 1, wherein the first silicon oxide layer also includes a third region between the first region and the conductive layer, and a concentration of the impurity in the first region is higher than a concentration of the impurity in the third region.
 6. The semiconductor storage device according to claim 1, wherein the first silicon oxide layer is in contact with the plurality of first gate electrode layers.
 7. The semiconductor storage device according to claim 1, wherein the first silicon oxide layer is in contact with the conductive layer.
 8. The semiconductor storage device according to claim 1, further comprising: an aluminum oxide layer between the first charge storage layer and the plurality of first gate electrode layers and between the first silicon oxide layer and the plurality of first insulation layers.
 9. The semiconductor storage device according to claim 1, further comprising: a third insulation layer between the first silicon oxide layer and the plurality of first gate electrode layers, wherein the third insulation layer comprises aluminum oxide or aluminum nitride.
 10. The semiconductor storage device according to claim 1, further comprising: a fourth insulation layer between the first silicon oxide layer and the conductive layer, wherein the fourth insulation layer comprises aluminum oxide or aluminum nitride.
 11. The semiconductor storage device according to claim 1, further comprising: a second silicon oxide layer between the conductive layer and the plurality of second gate electrode layers, the second silicon oxide layer containing the impurity.
 12. The semiconductor storage device according to claim 11, wherein a concentration of the impurity in the first silicon oxide layer is substantially the same as a concentration of the impurity in the second insulation layer.
 13. The semiconductor storage device according to claim 1, wherein each of the plurality of first gate electrode layers comprises tungsten, and each of the plurality of second gate electrode layers comprises tungsten.
 14. The semiconductor storage device according to claim 13, wherein the conductive layer comprises tungsten.
 15. The semiconductor storage device according to claim 1, wherein the conductive layer comprises tungsten.
 16. The semiconductor storage device according to claim 1, further comprising: a semiconductor substrate, wherein the first stacked body and the second stacked body are on the semiconductor substrate, and the conductive layer is in contact with the semiconductor substrate.
 17. The semiconductor storage device according to claim 1, wherein in a cross section along the first direction, the first silicon oxide layer includes a plurality of protrusions protruding towards the plurality of first gate electrode layers, respectively, in a second direction perpendicular to the first direction.
 18. A semiconductor storage device, comprising: a first stacked body including a plurality of first insulation layers and a plurality of first gate electrode layers that are alternately stacked in a first direction; a first semiconductor layer extending in the first stacked body in the first direction; a first charge storage layer between the first semiconductor layer and the plurality of first gate electrode layers; a second stacked body including a plurality of second insulation layers and a plurality of second gate electrode layers that are alternately stacked in the first direction; a second semiconductor layer extending in the second stacked body in the first direction; a second charge storage layer between the second semiconductor layer and the plurality of second gate electrode layers; a conductive layer between the first stacked body and the second stacked body and extending in the first direction and a second direction perpendicular to the first direction; and a first silicon oxide layer between the conductive layer and the plurality of first gate electrode layers, the first silicon oxide layer containing an impurity that is at least one of phosphorus, boron, carbon, and fluorine, wherein the first silicon oxide layer includes a first region and a second region provided between the first region and the conductive layer, and a concentration of the impurity in the first region is higher than a concentration of the impurity in the second region.
 19. The semiconductor storage device according to claim 18, wherein a concentration of the impurity in the first region is in a range equal to or greater than 1×10¹⁷ atoms/cm³ and equal to or less than 1×10²¹ atoms/cm³, and a concentration of the impurity in the second region is in a range less than 1×10¹⁷ atoms/cm³.
 20. The semiconductor storage device according to claim 18, wherein a concentration of the impurity in the first silicon oxide layer is higher than a concentration of the impurity in the first insulation layer. 